The present disclosure relates to optical encoder systems that include a structured code wheel.
Reflective optical encoders can be used to detect motion, for example, of a rotating code scale (e.g., a cylindrical code wheel) that includes a pattern of stripes to reflect light in a known pattern. Motion of the code scale can be detected optically using a light emitter and a light detector. As the code scale rotates, the intensity of light reflected by the code scale varies. In particular, light is reflected by the pattern on the code scale such that an alternating pattern of light and dark, or high and low intensity, can be detected by the detector. The detected pattern can be converted, for example by a signal processor, into a digital signal that is indicative of the movement, position, direction or velocity of the code scale.
In order to obtain a high quality signal at the light detector, it is desirable that the contrast between the levels of light reflected from the different regions of the code wheel be relatively high. Small changes in the relative positions of the code scale with respect to the light emitter or detector can contribute to a less-than optimal contrast.